The present invention relates generally to toggle switches and particularly to toggle switches of the kind that require a particular manual action to reset the toggle switch from one state to another. Such switches avoid accidental setting, and require a deliberate action on the part of an operator to change state.
Such switches usually involve a stem or lever arm to be moved or rotated as a lever from one position to another to be set in another state. Before moving the stem or lever arm, however, a detent must be released to permit the movement, and when in the new position, a detent is again engaged to prevent accidental setting of the lever arm to an undesired state. Such a construction is particularly desirable where the switches are small and installed close together, so that a setting of one might lead to an undesired or unnoticed setting or resetting of another, adjacent switch.
In the construction of such switches, in sub-miniature size, the lever arm has been constructed and installed in such a way that it is restricted to swing in only one plane to operate the toggle switch reliably. To provide such a restriction different means have been employed. One is to drill a hole in the lever arm or stem through which is inserted a pin to serve as an axle about which the lever arm rotates. Thus, when the lever arm is rotated to one extreme position it sets the switch in one position, and when rotated to the other extreme position it sets the switch in the other position, and always acts in one plane.
A second manner of construction is to mill two flat portions opposite each other on the lever arm. These portions are guided by inner cooperating surfaces of the housing to restrict the motion of the lever arm substantially to a single plane.
In both instances, typically, a pin is inserted in a transversely drilled hole in the lever arm at its upper, or outer end. The pin is captured within an internally threaded cap which is screwed to a detent element. The detent element is slotted at its upper end to receive the pin in the slot, so that the detent element is always oriented at a fixed element with respect to the lever arm. The detent element carries at its lower end a pair of downward projections or tongues at each side of the lever arm axis. The spring under compression urges the detent element downward to engage the tongues in corresponding slots in the housing which define the toggle lever positions, and thus, a detent is formed keeping the lever arm in position unless the detent element is raised to release the detent for lever arm movement. The handle may be raised against the spring compression to disengage the detent element, and thus, to withdraw the tongues from the slots, and the lever arm may then be rotated in the restricted plane, either by virtue of the axle or of the flattened guide surfaces, to the new detent position, whereupon the handle is released, and the spring drives the detent projections into engagement with a different pair of slots in the housing to prevent inadvertent motion of the lever arm.
Such sub-miniature detent protected switches are exemplified, for example, by a toggle switch sold by Apr., Siege Social ET Usine 82270 Montpezat-De-Quercy, France as models 5636-2V or 5639-3V or by a toggle switch sold by Fujisoku Electric Company, Ltd. 1890 Kizuki Sumiyoshi-cho, Kawasaki-Shi Japan as models MTL-106D or MTL-106E.
It has also been proposed in U.S. Pat. No. 2,885,905 of May 12, 1959 to Larkin and U.S. Pat. No. 2,723,571 to Koenig of Nov. 15, 1955, to provide detachable lever locks on toggle switches of conventional dimensions, the lever locks being threaded on the cylindrical bushings and overhanging in the manner of a cap so as to be impractical if used in close packed, sub-miniature, circuitry.